The present invention relates to a paper sheet stacking apparatus and a paper sheet post processing apparatus that conducts paper sheet post processing operations after image forming operations are completed.
Recently, there has been proliferated in the market a paper sheet post processing apparatus that applies the post processing, such as a bind processing, etc., to a bunch of paper sheets including a plurality of paper sheets stacked on the paper sheet stacking tray mounted in an inclined state, as a peripheral apparatus to be combined with a high-speed image forming apparatus, such as an electro-photographic image forming apparatus.
Further, in order to minimize the size of the paper sheet post processing apparatus and to smoothly conduct the high-speed processing, there has been a tendency to increase the angle of inclination for mounting the paper sheet stacking tray.
In the paper sheet post processing apparatus provided with such the paper sheet stacking tray mounted in the inclined state, paper sheets stacked on the paper sheet stacking tray, are apt to float up. Accordingly, sometimes, a paper sheet, floating up from the tray, impedes conveyance of the following paper sheet, and therefore, it becomes impossible to smoothly conduct the conveying and stacking operations of the paper sheets.
Patent Document 1 (Tokkai 2003-20154, Japanese Non-Examined Patent Publication) sets forth a solution for preventing such the conveying and stacking failures, in which a floating up action of the upper end portion of the paper sheet is suppressed by raising a center portion of the paper sheet in a conveyance direction.
According to the Patent Document 1, by raising a center portion of the paper sheet, a floating up action of the upper end portion of the paper sheet is appropriately suppressed, and the paper sheet is smoothly introduced onto the paper sheet stacking tray.
According to the Patent Document 1, the ejection nail for ejecting the paper sheet is employed for raising the center portion of the paper sheet. In such the configuration, the ejection nail moves from the initial standby position to the push-up position at which the center portion of the paper sheet is pushed up, and when ejecting the paper sheet, further moves to the supporting position at which the ejection nail supports the lower end portion of the paper sheet.
Referring to FIG. 1, the movement of the ejection nail will be detailed in the following.
Since a standby position X2 of an ejection nail X1 is located in the vicinity of the lower end portion of a paper sheet stacking tray X3 and is far apart from a paper sheet push-up position X4, the moving distance of the ejection nail X1 for moving in the clockwise direction shown in FIG. 2 from the standby position X2 to the paper sheet push-up position X4 driven by a belt X5 becomes long, resulting in an increase of the moving time period. In addition, the time interval for moving in the anticlockwise direction from the paper sheet push-up position X4 and passing through the standby position X2 and arriving at the ejecting position at which ejection nail X1 contacts the lower end of the paper sheet also becomes long.
Accordingly, there has been a problem that the abovementioned configuration could not cope with the stacking operation of the paper sheets currently conveying at a high speed.
Further, in order to stack a lot of paper sheets, namely, about 100 paper sheets, onto the paper sheet stacking tray X3, the height of the ejection nail X1 should be set at a value more than 20 mm. However, when the height of the ejection nail X1 is increased, since the height of the protrusion of the paper sheets pushed up by the ejection nail X1 becomes too high, the introduction path of the paper sheet is narrowed, and, sometimes, it becomes impossible to smoothly introduce the paper sheet onto the paper sheet stacking tray X3.